CURLOPT_SSL_CIPHER_LIST(3) Library Functions Manual
NAME
CURLOPT_SSL_CIPHER_LIST - ciphers to use for TLS
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CIPHER_LIST, char *list);
DESCRIPTION
Pass a char pointer, pointing to a null-terminated string holding the
list of cipher suites to use for the TLS 1.2 (1.1, 1.0) connection. The
list must be syntactically correct, it consists of one or more cipher
suite strings separated by colons.
For setting TLS 1.3 ciphers see CURLOPT_TLS13_CIPHERS(3).
A valid example of a cipher list with OpenSSL is:
"ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:"
"ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305"
For Schannel, you can use this option to set algorithms but not
specific cipher suites. Refer to the ciphers lists document for
algorithms.
GnuTLS has the concept of a [priority
string](https://gnutls.org/manual/html_node/Priority-Strings.html)
which has its own syntax and keywords. The string set via
CURLOPT_SSL_CIPHER_LIST(3) directly influences the priority setting.
Find more details about cipher lists on this URL:
https://curl.se/docs/ssl-ciphers.html
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
DEFAULT
NULL, use built-in list
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
This option works only with the following TLS backends: BearSSL,
GnuTLS, OpenSSL, Schannel, Secure Transport, mbedTLS, rustls and
wolfSSL
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_SSL_CIPHER_LIST,
"ECDHE-ECDSA-CHACHA20-POLY1305:"
"ECDHE-RSA-CHACHA20-POLY1305");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
HISTORY
OpenSSL support added in 7.9. wolfSSL support added in 7.53.0.
Schannel support added in 7.61.0. Secure Transport support added in
7.77.0. BearSSL support added in 7.83.0. mbedTLS support added in
8.8.0. Rustls support added in 8.10.0.
Since curl 8.10.0 returns CURLE_NOT_BUILT_IN when not supported.
AVAILABILITY
Added in curl 7.9
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_PROXY_SSL_CIPHER_LIST(3), CURLOPT_PROXY_TLS13_CIPHERS(3),
CURLOPT_SSLVERSION(3), CURLOPT_TLS13_CIPHERS(3), CURLOPT_USE_SSL(3)
libcurl 2025-04-16 CURLOPT_SSL_CIPHER_LIST(3)
curl 8.13.0 - Generated Wed May 7 16:25:36 CDT 2025